Means for drilling



SePt- 22, 1959 L. A. MARTINI 2,905,439

MEANS FOR DRILLING Filed Feb. e, 1957 2 sheets-sheet 1 A GENT sept. 22,1959 Filed Feb. 6, 1957 L. A. MARTINI MEANS FOR DRILLING 2 Sheets-Sheet2 INVENTOR.

L60 A. Mar/'m' AGENT United States Patent MEANS FOR DRILLING Leo A.Martini, Dallas, Tex. Application February 6, 1957, Serial No. 638,652Claims. (Cl. Z55-4.4)

This invention relates to a method of drilling and means therefor, andmore particularly to -a method and means for alternately increasing anddecreasing the relative downward pressure exerted by a drill string on abit mounted on and rotated by the latter on the bottom of a subterraneanbore.

The present application is `a continuation-impart of my priorapplication, now abandoned, filed November 7, 1955, and designated bySerial Number 545,25 6.

In the exploration for oil, the art of drilling well bore holes intosubterranean areas of the earth has been widely investigated andextensively developed. The techniques employed are many, and a widevariety of drilling bits and associated apparatus have been developed.One conventional procedure is to attach a suitable bit on the end of apipe string and to rotate the bit by the rotation of the pipe string. v

Thus, at the present time, the majority of drilling operations areconducted by employing rotary ldrilling equipment. In conventionalrotary drilling, a hollow, jointed steel shaft `called the drill 4stemis rotated from the surface of the earth. This shaft, extendingdownwardly into the earth to any desired depth, rotates a drill bit. Fora number of purposes, a weighted fluid called drilling :mud iscirculated in one direction through the drill stem :and in the oppositedirection .through the annulus between Ithe `drill stem and the borehole.

In the past, cable drilling equipment also has seen wide use and hascertain advantages, particularly where drilling in rock, but hasgenerally been displaced by rotary drilling which is especiallyadvantageous because it gives a high speed of penetration in relativelysoft formations, and because it is suitable for use at great depths.Rotary drilling, however, is relatively inefficient in very hardformations, since rotary bits, even of the hard-faced or diamond-settypes, are in such cases subject to a high rate of wear and requireconstant replacement. Cable tools, while most eifective in hardformations, are limited in their use to relatively shallow depths.

Previous proposals have contemplated giving -a reciprocating 4action toa rotary drill bit, and this has been done in several cases bymechanisms which raised and then dropped a b-it relative to the borehole and to the drill string rotating the bit. While without doubtpossessing merit, these mechanisms have tended to be costly and were toa certain extent subject to misalignment and to malfunctions caused bydenting or bending of relatively long cylinders, piston rods, etc. withwhich they were provided. By necessity, they also tended to be expensiveand complicated in construction and operation.

It is accordingly an object of the present invention to provide animproved method for alternately increasing and decreasing the relativedownward pressure exerted by a drill string on a bit rigidly mounted onsaid drill string and rotated by the same at the bottom of a bore hole.

Another object is to provide an improved method whereby elastic,elongating deformation is repeatedly .elected in the drill string andeach time followed by 2,905,439 Patented Sept. 22, 1959 ice elasticrecovery of the drill string for increasing and decreasing its relativedownward pressure on the bit.

A further object is to provide means whereby the impacting action of acable tool is added to the grinding action of a rotary bit.

Yet another object is to provide means for elfecting repeatedelongations, with-in its elastic limits, of a string of drill pipe onwhich is rigidly mounted a bit, each of said elongations being followedby elastic recovery of the drill string.

Still another object is to provide means such as stated above which arehydraulically operated by the drilling fluid customarily supplied to thebit.

An additional object is to provide means such as thus far stated inwh-ich the bit is mounted on the drill string rigidly and not throughtelescoping parts, thus assuring al-ignment of the bit and preservingits ability to drill a straight bore.

Still another object is to provide means of the above character whichare simple and automatic in operation,

relatively easy and inexpensive to construct, and provided withlubricated and otherwise protected parts which as a consequence have along working life.

Other objects and -advantages will become apparent from thespecification and `claims and from the accompanying `drawings whichillustrate an embodiment of the invention.

Briefly stated, the invention comprises a method for alternatelyincreasing and decreasing the relative downward pressure of a hollowdrill string on a drill bit rigidly mounted thereon while the bit isrotated by the drill string at the bottom of a bore hole, this beingaccomplished by elastic, elongating deformations of the drill stringfollowed by elastic recoveries of the same which are produced byalternately restricting and allowing substantially unimpeded ilow ofdrilling uid Ithrough the drill string at a point considerably removedfrom its upper end. The invention further provides an eicient anddesirable means for Iimplementing the use of the above method. The majorelements of these means include: a continuous passage extending througha drill string and a bit mounted on the lower end thereof; highpressuremeans for supplying drilling fluid to the passage in the region of theupper end of the drill string; valve means in the passage at a`considerable distance from the upper end of the drill string; resilientmeans for biasing the valve means toward van open position thereof; andautomatic means for varying the bias exerted by the resilient means onthe valve means. The valve means is movable by drilling fluid ilowingthrough the continuous passage to a position wherein it substantiallycloses the passage. The automatic means may comprise an elongatedtubular part rigidly mounted in the continuous passage, closed at itsupper end, and having restricted communication at or near its lower endwith the continuous passage. A piston slidably mounted in the tubularmember is biased toward the lower end of the latter by means containedin the tubular member. This piston is operatively connected to theresilient means biasing the valve means and is movable, by pressure offluid entering the tubular part, to a position wherein the valvebiasingmeans forces the valve means out of its position substantially closing`the passage and to a position wherein ow through the passage issubstantially unrestricted. The piston is also movable, by the meansbiasing the same, to a position wherein the valve-biasing means allowsclosure of the valve means by the drilling fluid. Connection between thevalve means and the resilient means biasing the same may be aiforded bya substantially non-stretchable member, such as a rod, slidablyextending through the piston and the lower end of the tubular memberinto the interior Vof the latter above the piston. Wear on the valvemeans is minimized by provision'thereon of la resilient coating, andmeans is furnished for lubrication f the piston and the memberconnecting the-valve means to its .biasing resilient means. Ina[preferred embodiment of |theinvention,'.the .valve means' and automaticmeans'are enclosed in 1an outer cylinder through Hwhich the continuouspassage' extends ndin'coinbination with which '-they-formatool which mayberigidly mounted in a drill-string asaserial member thereof forinstance, thetoolmmay constitute the lower member of a'drill string .andmay have the bit rigidly mounted on'itslowerl-.end,` or Ialternativelymay be mounted in Vthe drill string at some distance'above 'the bit.When the drilling uid closes the valyefmeans, hydraulic pressurelis'built up in the'fdrill stringY by the highpressure Vsource ofdrilling ilnid. This pressure effects elastic .elongation of( the drill.string above -the valve, -fthus increasing downward pressure fof the idrill string on the bit.` While the valve means remains'closed, drillingfluidmoves thepiston'toa position wherein the bias'on the Valve means'isso increased 'that it'is vforced open. When thisoccurs,.uid,pressure-inthe continuous passage is relievedasiluiditlerein 'resumes unrestricted ilow; `-the drill string achieveselastic recovery to Vits original length; and the piston is moved byitsl biasing means backV to Va position .wherein bias ,on the `valvemeans is small enough to la'gainallow .closurefof'the latter. i i f Inthe drawings, which illustrate. a preferred embodiment of the invention:A Y Y Figure l is a semi-diagrammatic View showing the drill string,high-pressure source. of drilling'fluiitool, and bit, the latter beingin place in aV subterranean bore;

Figure 2 is a longitudinal sectional View of the tool, bit, and afragment of theldrill string taken along line lll- II of Figure l; and IFigure is a cross-sectional view taken at the location designatedbyline'lIl--lllof Figure 2 With reference nowto Figure 1, -a drillingfacility includes a xture =rotatably supporting a drill string 1:1, thelatter being madev to rotate by va power-driven table 12 of anyconventional sort. The drillstring 11 extends downwardly into asubterranean bore 1 3,- and rigidly mounts the elongated vtool '14. Onthe lower end of the tool I4. may be mounted an additional section ofdrill pipe similar to 11; or, as `showin-the bit 15 may be securely fandrigidly mounted ldirectly on the lower end of the tool. The `drillstringvll, as will be further shown and described, is hollow and thuscontains a passage utilized for supplying drillingtluid to the bit 1'5.This passage (lated more fully described) receives drilling fluid from ahigh-pressure pump 16 through a suitable conduit I17 which has juncturewith the drill string 1'1 at a pointY preferably near the upper -end ofthe. latter. The pump 16 must be capable of delivering iluid to thedrill string |11 at pressure such that, With vthe flow of fluid stoppedat the tool 14, the hydraulic e pressure built up within thedrill stringwill be sufficient to effect enough elongating, elastic deformation ofthe same tosubstantially increase its relative ,downward pressure on thebit andfthus effect 'a corresponding increase in the,pressu re of therotating bit 1'5 .on the bottom of the bore 13.

-With added referenceto Figure -2, the drill string 11 has a hollowinterior 118 which extends from the -tool 14 to thepreviously describedjunctureof the drill string with the drilling-fluid supplying conduit17.

The toolf14has an outer cylindrical part 19 preferably .provided withfemale threads v20. at its lower end for reception of matchingthreadsprovided on the upper end of thebit 15 and with,y male threadsf21on its .upper end for engaging the female threads: customarily providedin the lowerrend of the drill string 11. The' internal diameter of theouter cylinder v19 mayvarysasbest suiting aparticular application, andconveniently may? be madei larger than that of the drill string. 1'1. Ataxmiuimllmit. and

parts therein should not unduly restrict the llow of drilling iluidwhich it will be apparent iiows therethrough from the drill string 11 tothe bit i15, the interior of the outer cylinder 19 being open to andcontinuous with the interior 118 of the drill string =1.1. At its upperand lower ends, the outer cylinder 19 may be of an internal diameterapproximately that o f the drill strings interior 18. An annular seat Z2'is-provided near the lower end of the outer cylinder 19- abovethethitfengaging lower threads 20. This seat 22 defines an openingtherethrough which provides communication "between the'i-nte'rior of theouter cylinder 119 and an .axialpassage 23 fin the .b itleS. In thespecific eramplefthe iiterir f the outer cylinder 19 has anupper-segment 124 whichextends downwardly to a point convenientlylocated somewhat below the upper threads 21. From this point, thecylinders internal bore llares downwardly and outwardly to the fulldiameter of its maior. oootfal,Porflon,-%,-Wbiob dlairlotor llollloboSolllbilit for .Proporbboommolotlon otiolornalpafts. to be described.yFor' the lower endotfl V4his eritralportion 25, the lowerportion21S-.of thebore mayfdiverge dewnf wardly and inwardly to. the seatvzg,

The seat 22 will best withstand the abrasive' etffeetspf drillingHohl-.passing tborotllrollsllaotlftbo uoariiposod thereupon bytboxrolvofbolyl?. (tobo-dosoribtd) ifi! is made from orcoveredbyalayero(t material Such as onoiofbororioos. Sorts ofoatof, rubbers or otoogbg'olastoraorlo controlled. sob.-

ooo. of tho lluorooarbonolastomore. an. orafflol l which, biblia.-uorolbylooo. Probabili matliotosl- Toonf 'Tho convergent loworfsoeoioot2,6 of'lbo. la? iorior of thooutor oylndor -1s91islmaol1i d torrovidoo oshort counterbore 2.8 offaysizefer .snug eception ovfithe, seat 22 andon the lower end of whiehwthefseathnds support. y

For easeof, installation: ofjcornponents. installed therein, the outeroylindor 19. *11i-arbo modo" :oo Sootiolis.. 292 30, 31,- Tbus,tliooppbrfboromortloo @and tho lloro therebelowmay be containedima-relatively short, upper? ond Section 2? -Aoorrosporloiog.loworondfsootionrl may Contain the soot. llano tbolborob;dii/.oreille ,lower Portion 26.- yThosoobotforlo 12.9., Slohobldbotllroaooslfas al 32 Vand 33foi' oogagemootwthfoort odios threads of amaior, obntmljportion 3,0. rbiolroo roo tho, Qontrol largerdianieterboro portion 2.5:,

A11 inner oylndrloloort is risidlrf,(andprotorably ooaxallyl mountedirlthoolltorloylinolor: for thi Por: pose it iS-provdodwithoilotipborolly.dlopooosotfof lugs 36 loolool atorrloor its., oppor.ood. and .has a similarfsn V37 CFiguro. 3;) profe ably looatlodfat-otnobr ils lower ond., Theologe-3.6., 3. oy bofatlxodito lille innerCylinder; .3'.5 in any. Soollro and. .uitablo'fashion.- (fon example bywoldtirigl ,l andA mustfbotlonseonoosh. tfbrioo fully the3 intervalbotwoo11-tllo-1wa1lsfof-lho two oylirlsof 19,65.. Thermes-.36, S'lraotopaoors-wbiohlrosltvoly prevent t lateral motion. otltbo, loneroylilldor. litl; tho outer cylinder-119,. 11nd,-.t11otoppor-logs.- Morermly lrotained against relativo ondwiso; motion of hof two Cyl.'- inders35, 1.9i This 'lattorfproferably is,-aooomolioboo by counterborirlg thoootoroyliilsor, 1.9, at its oppor .ono to. form anintornal shoulder 3.4looafoslabolowtllotlouor end. olI the; threads. 52 of: theoppor-oodlsootior'?, .fTho upperloss 36 aro rigidly olompod .bota/ oontbowshoulslor 34. and tho upporfond Sootion 29.2 Barberi. otr loroV 36;37 .may comprise three ornato-memberseiner Elgar-o3 Shows tho bottom-sotto hai/oi four lugo Webtools/forested about tho periphery of 'tho-rlnoroy Hor 3,5-,

Astho inner cylindorhaszanovo dialnetorfwhiob is substantiallySmollorlhon. tho -innor'diamotortfofttho coaxial.. outer oylindor 1.9, as lobi'o'rlilso. Space 38; between the' juxaposed-walls yofQthQSeYcylinderS, fThis space v38v is continuousvwith theinterierofvtheouter cylinder 19.belovvand abovo @bionet-Cylinder 35 .aotlhus iscontinuous with. theblbioloriorziligoro 2).-and tho drillstring interior1t?, all tbosooooorrlingly boina-parts of a single, continuous passage39 which extends through the drill string 11, tool 14, and bit 1'5.

A piston 40 (Figure 2) slidably mounted in the inner cylinder 35 has acentral, axial opening 41. Appropriate grooves are provided in thepiston 40 around its periphery and within the opening 41 for receivingsealing rings 42A and 42B. The outer rings 42A seal between the pistion40 and the wall of the inner cylinder 35; the inner rings `42B sealbetween the piston and a rod 43 to be described.

The inner cylinder 3'5 is closed at its lower end by a circular wall orplug 44 which is peripherally threaded for engagement of correspondinginternal threads 58 formed in the lower end of the inner cylinder. Theplug 44 has a central opening -45 which is coaxial with and of the samesize as the central opening 41 of the piston 40. The material of theplug -44 defining central opening 45 is provided with one or moregrooves coaxial with the opening 45 and utilized for receiving one ormore sealing rings y50. Radially displaced from the plug opening 45 areone or more restricted passages or orifices 46 which communicate betweenthe continuous passage 39 and the lower face of the piston 40. Theseorifices 46 may be in the form of passages drilled through the plug 44and opening beneath the piston `40. Four such orifices 46 are shown inFigure 3.

A helical spring 47 (Figure 2) mounted coaxially with and in the innercylinder 35 between the piston 40 and' a wall 48 which closes the upperend of the inner cylinder constantly urges the piston 40 toward the plug44, which acts as a stop for limiting downward travel of the piston.This spring 47 is a component of a first, piston-biasing resilient meanswhich further includes the air or other compressible iiuid trapped abovethe piston 40 and compressed by the same when it is moved upwardly.

The rod 43 has an enlarged upper end which may include a cross-piece 49located interorly of the inner cylinder 35 and above the piston 40. Therod 43 extends downwardly through the piston and plug central openings41, 45 and should be of a diameter such that it is axially slideable inthose openings, yet Well sealed by the Sealing rings 42B, 50. A passage51 preferably provided in the rod `43 communicates between the interiorof the central hole 45 of the plug 44 and the interior of the innercylinder 35 above the piston 40. Threads 52 are formed on the lower endof the rod.

A tapped valve body 27, preferably of circular form, is rigidly attachedon the lower, threaded end of the rod 43 is coaxial relation to thelatter and the seat 22. The valve body 2'7 is of such diameter that wheninserted into the seat 22 it snugly lls the same, thus interruptingthereat the continuous passage 39. In the example shown, the valve body27 is made in the form of a sphere/of greater diameter than the seat 22,has a metallic core 54, and has an external skin or covering 55 made, asis the seat 22, of any durable, preferably resilient material such aspreviouSly mentioned.

The valve body 27 is biased upwardly away from the seat 22 by a secondresilient means comprising a yhelical spring 56 footed on the piston 40,coaxial with the rod 43 and the piston spring 47, and engaged at itsupper end by the rods vcross-piece-49. The valve spring 56 is of smallerdiameter than the piston spring 47. Connection between the valve body 27and its spring 56 is` effected by the rod 43. This spring 56 may be madeof a material which is rectangular in cross-section in order that it maybetter endure axial loads, imposed after its full compression, withoutbuckling.

-It thus may be`seen that the spring 5,6 is a resilient means whichurges the valve body 27 away from the valve seat 22, and as the spring56 is footed on the piston 40, upward movement of the piston 40 willtendto compress the spring 56 and consequently increase its upward force onthe valve body 27 through the rod 43. Y

At this point, it may be noted that the plug 44 is preferably of suchthickness that the lower end of the oil passage 51 will not leave theplugs central hole 45 when the valve body 27 is moved to its upmostposition. This is desirable for the prevention of the delivery of oil tothe inner cylinder 35 below the piston 40 via the passage 51 The bit 15may be of any sort well suited for rotary drilling and provided with apassage 23 communicating as described with the interior of the outercylinder 19 and opening, near its bottom, into the wellbore 13 (Figurel).

From the above, it will be seen that, in the example shown, the valvemeans includes the valve body 27 (Figure 2) `and seat 22. The resilientmeans for biasing the valve means toward its open position is thesmaller-diameter spring 56. The rod 43 provides a means for con--necting this resilient means to the valve body 27. The

automatic means for varying the bias exerted by this,

resilient means on the valve means includes the inner cylinder 35,piston 40, and the spring 4'7'and volume of compressible fluid above thepiston 40. `It will be understood that the valve means may be located atany point in the drill string 11 (Figure 1) which is far enough removedfrom the upper end of the latter to secure sulicient elongation of thedrill string during operation (to be described) of the device. Thus, thevalve means, automatic means, and valve-biasing resilient means may belocated in a drill bit made to receive them. Alternatively, the valvemeans may be located in the bit 15 (Figure 2) and the automatic meansand valve-biasing resilient means in the drill string 11 immediatelyabove the bit, connection between the valve means and its biasingresilient means being maintained by the rod `43.

On the other hand, as in the example shown, the valve means, itsresilient biasing means, and the automatic means may be located at thelower end or within the length of the drill string 11. To pro-vide asturdy, troubleree mechanism, it is generally desirable to make theinner cylinder 35, valve seat 22 and body 27, etc. of generous size, andthis is made possible by locally enlarging the diameter of thecontinuous passage 39. To this end, the outer cylinder 19 may be madelarger in diameter than the balance of the drill string 11, and theresulting structure comprises a tool 14 which may be rigidly installedin the drill string 11 to form a serial member thereof.

The operating life of the device will be prolonged by lubricatingsliding of the rod 43 through the piston 40 and plug 44 and of thepiston 40 through the inner cylinder 35. To this end, a layer oflubricating fluid 57, such as a suitable mineral oil, is provided in theinner cylinder 35 above the piston 40. Oil on the cylinder walllubricates movement of the piston 40 thereagainst, and oil on the rod 43similarly facilitates sliding of the latter through the piston 40. Theoil passage 51 in the rod 43 is preferably made long enough so that,with the piston 4) near the plug 44 and the valve body 27 seated, itsupper end is above the level of the oil 57, while its lower end remainswithin the plugs central opening 45. The upward extension of the oilpassage 51 must be limited to a dirnension such that its upper end willbe submerged in the oil 57 before the piston 40 has entirely reached thetop of its stroke.

plugs central opening 45. Although such is not shown, this lubricationof the plug 44 and rod 43 may be improved, when found needful, by theinclusion of a wick, such as is well known, in the oil passage 51.

In operation, the bit is rotated in well-known fashion on the bottom ofthe bore 13 (Figure l) by the table 12 and drill string 11. The pump 16delivers a flow of drilling uid through the conduit 17 and continuouspassage 39. (Figure 2) to the bottom of the bit 15 for improvingoperation ofthe latter.

As the stream of drilling fluid flows through the continuous passage 39past the valve body 27, it exerts forces upon the latter which move itdownwardly against resist-` The passage 51 thus receives oil 57 which isde-V livered through its lower end to the wall defining the anceof thevalve-biasing spring 56. As thevalvebody 27 nears the seat 22, therestriction it imposes uponlthe flow of 'fluid rapidly increases. Thepumpcontinues to supply fluid to the drill string at -a -rate which, butfor the resttiction of the flow by Ithe valve body 27, would beunchanged. As a consequence, fluid pressure in the continuous passage 39above the valve body 27 increases, while it tends to decrease belowtheibody 27. 'The sharply increasing vpressure increment across thevalve lbody'' causes the linalvportion of its-downwardstroke-to be quiterapid, and it therefore seats with asna-p, whereuponv the downwardmomentum ofthe drilling'fluid and therapid increase of hydraulicpressure which -is effected by the continuously running pumpexert-strong forces internally of -the continuous passage 39 above the-valve seat 22 rwhich effect an elastic elongation or stretching of thewholedrill string 1-1 above the valve seat. Thus, some'of the inertia ofthe drilling uid and weightfof'the drillstring 1.1, sustained bythe-supporting meansflll (Figure l.) before the stretching, istransferred with asharp -impact to the bit 15 (Figure 2). Sincethearnount of lengthwise stretch for a given linear foot lof the drillstring Y11 will be -quite small, it is obvious that thelvalve meansmus-tbe located a considerable distance lbelow-the top offthe continuouspassage 39 in order that the total-tendencytoward elongation experiencedalong the Vdrill string 111 -will Ybe large enoughto yield the desiredincrease of-d'ownward pressure on the bit 15.

As soon as-pressure in the continuous passage -39 rises high enough toovercome resistance olered bythe -piston-biasing spring 47, lluid beginsto ilow-into-the -inner cylinder 35 from the passage 39 'throughtheivorilices 46 in the lower-end wall 44. This flow raises the piston40 against pressure of the piston-biasing spring 47--and air orothercompressible fluid in -the inner cylinder 3-5 above the piston. Inmoving upward, the piston .-40 also must -further compress thevalve-biasing spring 56, and in so doing it increases the force vwithwhich the valve lbody 27 is urged away from the seat 2-2. The lower-facearea of the piston 40 must "be large enough, relative to the valve body27, to ensure that downward forces on the vvalve body will be overcomebysupward forces exerted on the latter by thepiston through the rod 43and valve-biasing spring 56. The :rapidity Iwith which 'this occurs isregulated -by the vcolleetiv'ejsize of; the orifices 46. Thus, if theorilices Adare smaller, the allow-of duid throughthemfinto the innercylinder will be slower, and a longer 'time interval willbeconsumedinraising the piston 40 to a point at which -downward forces Yon thevalve body 27 are-overbalanced.

`When the point just deiined-is reached,-the-valve body 27 will moveupwardly above the-seat 2,2. 3If this motion resulted in no pressurechanges in the continuous passage 39, the valve body 27 would moveupwardly only until Athe unchanged, downward forces exerted thereoncould come into equilibrium with-thevalve-biasing spring 56. As soonas'the valve body 27 moves alittle wayout of the seat 22, however, uidows yinto the -bit V15, thus relieving some of the pressure in theApassage 39 above the valve body. The pressure increment across thevalve body 27 is thus reduced, thus increasing-the net upward force Jonthe valve body. As the valve body 27 moves further upward, thisprocess'progressively continues 1until the valve body is ywell away from-the seat. Consequently, the spring 56 actually Vis able to move -thevalve body 27 quickly and vigorously l.to its open, 4fully raisedposition wherein it is well removed from thevalve seat 2-2. The fullVflow of -lluid into vthe bit 1'5 throughthe seat 22 thus is quicklyresumed, fluid pressure above the seat drops substantially to that inelectfbefore clo sure of the valve means, and the elasticproperties'o'ffthe material (steel, etc.) of which the drillstring vr11'is 'made eifect 'its It'ull recovery to its original length.

'Return of the piston 40 -to its position wherein-minimum force isexerted by the smaller-'diameter spring 56 on the valve lbody 2.7 is`etlected by the fluid and larger spring 47 compressed inthe innercylinder 35 above the piston `4|) and also, in some degree, by `downwardpressure of the smaller :spring 56. The rate at which the piston 40. 'isforceddwnward is limited by the rate of flowrofdrillingluidlout 'of theinner cylinder 35 through the oriiices vd6, and 'ihence is controlled bythe collective size .of sthe rlattei'.

When the lpiston 40 has travelled far enough downwardly for downwardforces exerted on the valve body 27 by the flow of drilling fluidthrough the continuous passage 39].to override v'the -upward force-exerted by the valve-'biasing spring 56, the valve -body 27`will bemoved downwardly'and .resseated in vthe seat 22. Thus, the whole .cyclewill Ioccur `over and rover again, and the Arepeated impactsV-andperiods of downward pressure o n the .bit 15, combined .withltheperiods in which elastic recovery of .theJdrill :string 111 occurs,vgive the bit a reciprocating actionkwhicln added to its Irotary action,much improved-ts oper-ation, especially in hard formations. I

'When the pump .is-shutoff to halt the flow -of drilling lluidrto the.drill string, fluid v.may not llow past vthe valve body 27 with enoughimpetus to force it `into the seat 22. In such a case, lall .drilling.liuid -will fbe automatically drained through the bit 15 until -no moreremains in the .continuous passage '39 or until it is level withdrilling uid Vin the well lbore. Where -the column Vof fluid issufficiently .'high, when `the pump is -shut oli, to cause seatingtof.the valve body 27, `the -device' will go through :its cycleiofoperation u ntil the' uid column `is reduced toa height at which Anotenough flow occurs to seat the'valve body 257. 'The remainder -of -vthelfluid then will drain into -thewell bore through theibit 1-5 withoutinterruption. 'Thesi'ze of the piston 40 is such that .the upward fforceit. can exert, when -ful l pressure of .the drillingud is .directed toit, 'is flarge enough lto achieve unseatingsof the valve body 27 at andbeyond all times that vthe .column of' uid is capable of reseating it,Thus', the valveibody-Z'f :always stops-operation while unseated, andfull drainage offthedrilling lluid through the bit 1'5.-when the .pumpis .shut off is automatically accomplished. 4

While the foregoing fully describesapreferred embodiment ofitheinvention, it vwill `=be `evidentAtha'tlrernoval of the largepiston-biasing spring .-47 `willlnot render the device inoperative, solong as the vsmaller spring 56 is of proper springarate andleugth, butinstead -will result in astill more vsimple andeconomically constructedform of the invention'. In operation of this form of the-invention, theinitial seating .of the `valve 'body 27 in the seat 22 occurs aspreviously deseribed,-and Athe piston 40l is .in the samewaydrivenupwardlyby `lluid rforced -thereagajnst `through theorices 46,.The upward movement of the vpistonfm) is, however, resistedfonly by thesmaller spring 56 andby. the air :entrapped above Vthe -piston 40 in theinner cylinder 35. Thus, the spring A56 isa resilient means for biasing.the `valveibody '27- to its open position and Aalso for :moving ithe-piston 140 toward lits lowermost .position wherein minimum bias Yisimposed upon the valve body. 2 7. Whenfthe piston 40 .has moved upwardlyto .a Apoint at which expansive forces in .the spring 56 overcome'downward --forcesV imposedy by the drilling iluid lon the vvalve body27., or -when vthe spring 56 becomes Yfully'compressed, the valve body27 -is moved upwardly as .-previouslydescribed and .is stopped initsupward Atravel -by contact with the bottom of the -plug 44. The piston40 then is moveddownwardly `by the energystored in the spring-56 and inthe'air compressed above the piston. 40. When-the lower end of thespring 56, footed onv'the piston 40, hasmoved downwardly far enough, aYpoint is reached -at which downward -forces exerted on the vvalve body2 7 'by' Athe yllow ofV drilling fluid override upward forces exertedonthe valve -body 27 by the spring l56, and at this point the valve body27 is seated as before against resistance of the spring 56. This cycleof operation continues as long as the flow of drilling iluid is suppliedto the continuous passage 39.

While a novel and efcient mechanism has been disclosed together with amodification thereof for carrying out the method of the invention, itwill be clear that the method is not restricted to application onlywhere a mechanism such as described is used for carrying it out.Instead, the method will be found advantageous whenever other ecientmeans which might be made available (for instance, an electrically timedand operated footvalve) are used, through it is doubtful that such othermeans could offer the advantages of the simple and efficacious meansherein provided. Other forms and modications of the present invention,both with respect to its overall arrangement and the details of itsrespective parts, which wi'll become apparent to those skilled in theart after reading the foregoing description taken together with thedrawing, are intended to come within the scope of the invention as moreparticularly set forth in the appended claims.

I claim: 1. For intermittently increasing the downward pressure of adrill bit on the bottom of a subterranean bore, said bit being rigidlymounted on the lower end of and rotated by a drill string supplied withdrilling fluid under pressure, a device comprising: a passage extendingthrough said bit and drill string and used for receiving and conductingsaid drilling fluid; a valve seat in said passage in the vicinity of thelower end thereof for the ow of said drilling fluid therethrough; avalve element upstream of said seat in said iluid and movable by ilow ofthe latter to a closed position wherein said valve means substantiallycloses said passage for allowing an increase of hydraulic pressure inthe latter which eiects elastic elongation of said drill string andthereby increases the pressure of said bit on the bottom of said bore; acylinder rigidly mounted in said passage, said cylinder having a first,closed end and further having a second end through which communicationis provided between the interior of said cylinder and said passage; apiston slideably mounted in said cylinder; and resilient meansinterposed between said piston and said valve means, said resilientmeans being operative for imposing a bias on said valve means toward anopen position thereof wherein said passage is substantially'unobstructedby the latter, and for biasing said piston toward a position thereofwherein said bias on said valve means is reduced to a value permittingmoving of said valve means to said closed position thereof by saiddrilling Huid, said piston being movable by said drilling fluid toanother position thereof wherein said b-ias forces said valve means toquit said closed position thereof.

2. Forl intermittentlyV increasing the downward pressure of a drill biton the bottom of a subterranean bore, said bit being rigidly mounted onthe lower end of and rotated by a drill string supplied with drillinguid under pressure, a device comprising: a passage extending throughsaid bit and drill string and used for receiving and conducting saiddrilling fluid; a valve seat in said passage in the vicinity of thelower end thereof for the ow of said drilling uid therethrough; a valveelement upstream of said seat in said fluid and movable by ow of thelatter to a closed position wherein said valve means substantiallycloses said passage for allowing an increase of hydraulic pressure inthe latter which eifects elastic elongation of said drill string andthereby increases the pressure of said bit on the bottom of said bore;resilient means for exerting a bias upon said valve means toward an openposition -thereof wherein said passage is substantially unobstructedthereby; a cylinder rigidly mounted in said passage, said cylinderhaving `a rst, closed end and further having a second end through whichcommunication is provided between the interior of said cylinder and saidpassage; a piston slideably mounted in said cylinder and operativelyconnected to saidresilient means for varying said bias exerted by thelatter on said valve means, said piston being movable by pressure ofsaid drilling fluid to a position wherein said bias forces said valvemeans to quit said closed position thereof, said piston being movable toa second position wherein said bias is reduced to a value permittingmoving of said valve means to said closed position thereof by saiddrilling iluid; and other resilient means biasing said piston towardsaid second position thereof.

3. A device of the character claimed in claim 2, said communicationbetween the interior of said cylinder and said passage being through atleast one opening provided inrsaid cylinder below said piston and of asize restricting the rate of a flow of drilling iluid into said cylinderwhich occurs when said valve means is closed.

4. A device such as claimed in claim 3, said other resilient meansincluding -a compressible fluid enclosed above said piston in saidcylinder.

5. A device `such as claimed in claim 3, said other resilient meansincluding Ia helical spring compressed between said piston and said rst,closed end of said cylinder.

6. For intermittently increasing the downward pressure of a bit on thebottom of a subterranean bore, said bit being rigidly mounted on androtated by the lower end of a two-ended drill string, an apparatuscomprising: a continuous passage in said bit and drill string, saidpassage communicating with said bore in the region of the lower end ofsaid bit; means for supplying drilling uid under high pressures to saidpassage in the region of the upper end of said drill string; a valveseat near said lower end of said passage and passed through by thelatter; a valve member movable relative to said seat by ow of said uidthrough said passage to a position wherein it substantially closes saidpassage and restriction of said llow by said valve member occasions anincrease in hydraulic pressure in said passage accompanied by elasticelongation of said drill string and increased downward `pressure of saidbit on the bottom of said bore; resilient means for exerting a bias uponsaid valve member toward an open position thereof wherein said ow offluid through said passage is substantially unrestricted by said valvemeans; and a movable member contacting said resilient means and saiddrilling fluid, said member being responsive to the pressurethereagainst of said fluid for moving said resilient means in accordancetherewith, said member being ,distinct from said valve member.

7. A well tool adapted for serving as the lowermost member of a l.drillstring rigidly mounting and rotating a bit at the bottom of asubterranean bore, said tool comprising: yinnerand outer tubular partsspatially xed relative to each other;` means for connecting upper andlower ends of said outer part to the lower end o-f a hollow drill stringand to the upper end of a bit having a passage opening into saidsubterranean bore; a chamber formed between said inner part and saidouter part, said chamber having free communication with the interior ofsaid hollow drill string; a seat in said outer tubular part providingcommunication between said chamber and said passage in said bit; apiston slideably mounted in said inner tubular part; means closing saidinner tubular part at an end thereof lying on one side of said piston;an orifice providing restricted communication between said chamber andthe interior of said inner tubular part on the other side of saidpiston; resilient means resisting movement of said piston away from saidorice; a valve body seatable in said seat for interrupting communicationbetween said chamber and said bit; and resilient means connected betweensaid piston and valve body and operative for urging said valve body awayfrom said seat.

8. A well tool such as claimed in claim 7, contacting surfaces of saidseat and said -valve body being covered by a durable, resilientmaterial.

9. In ,a .well drilling facility including a-drill-string having upperand lower-ends, `afhigh-pressure source of drlilling fluid, and -a bitrigidly mounted on the lower-end ofsa'id drill string and rotated-thereby -at vthe bottom -of a subterranean bore, 'a device comprising:`a continuous passage in said drill string and bit, said passage 'havingcommunication with-said subterranean bore in-the region of the lower endof said bit and connected inthe neighborhood of said -upper end of saiddrill string to said source of high-pressure fluid; an annular- -seatinsaid passage -and providing-communication between -upper and lowerportions thereof., said seat being remote -from-said upper-end of-saiddrill-string; an elongated tubular `member rigidly mounted in saidpassage above said seat and having an outside diameter substantiallysmaller than the diameter thereat of said passage, said tubular memberhaving a closed upper end-and a wall across its lower end; at least oneorice providing communication between said -passage-and the interior ofsaid tubular member through said-wall; a piston slideablein said tubularmember; means for sealing between said piston and said tubular member;first resilient means resisting movement of said piston Itoward saidclosed upper end of said tubular member; a rst opening extending fromsaid passage into said tubular member through said wall across saidlower end of the latter; a second opening coaxial with said firstopening and piercing said piston; a rod having upper and lower ends andextending slideably through said first and second openings, said upperend of said rod being adapted for engaging a helical spring; means forsealing between said rod and said Wall and between said rod and saidpiston; second resilient means comprising a helical spring compressedbetween said piston and said upper end of saidrod; and a spherical valvebody rigidly mounted on said lower end ofV saidy rod, said -valve bodybeing movable downwardly againstY resistance of -said second helicalspring -into said-"seat for substantially interrupting communicationbetween said upper and lower portions of said passage.

10. A device such as claimed 'in claim 9,' said -rst resilient meanscomprising a compressible uid contained in said tubular body -above saidpiston.

ll. A device such -as claimed -in claim `9, said first resilient -meanscomprising a helical spring compressed between said vpiston and saidclosed upper end of :said tubular body.

l2. A device such as claimed in claim 9, said first resilient meanscomprising a helical spring compressed between said piston and saidclosed upper end of said tubular body-and further comprising acompressibleuid contained in said tubular 'body above -aguantity oflubricating liquid lying on said piston.

13. In combination with a hollow drill string having upper and -lowerends., a high-pressure source of drilling liuid, and a Ibit rigidlymounted on the lower vend of'said drill string and rotatedthereby at thebottom rof Ia subterranean lbore, said bit having a passage ifor thereception of -drilling luid and for the discharge -of the same into saidzbore, a device comprising: an outer cylinder provided with means -forrigid connection thereof at its upper end to said drill string and atits lower end to said big-the interior of said outer cylinder havingcommunication with the hollow linterior of said drill string; an annularseat inl said outer cylinder near the lower end thereof, said seatdeiining an opening affording -communication between said interior ofsaid outer cylinder and sa'id passage -in said bit; an inner cylinderhaving upper and lower end walls and rigidly fmounted in saidl outer-cylinder in spaced, coaxial relation thereto; a Vpiston -slideablymounted in said Vinner cylinder; means forl sealing between said pistonand said `,inner cylinder; coaxial openings centrally piercing saidlower end wall' and said piston', a rod extending through Vandslideable` in said coaxial openings; means for sealing between -said rod.and said `piston .and lower end wall; a plurality of --restrictedopenings communicating between 'the `lower face of said piston -and theexterior of said inner cylinder; resilient means urging said pistontoward said -lower end'wall, said resilient means including acompress'ible fluid contained in said inner cylinder above said pistonand a helical spring compressed between said upper end wall and saidpiston; a helical spring footed on said piston and urging said rodupwardly; -a spherical body rigidly mounted on the lower end of said-rodand movable against resistance of said helical spring into said vseatfor interrupting communication between said outer cylinder and'saidpassage in said bit.

14. -A device such as claimed -inclaim 13, said device furthercomprising a lubricating liquid contained in said inner-cylinder abovesaid piston, said rod having a passage through which said lubricating`liquid is supplied to -said '-lower end wall where 'the latter is insliding contact with said rod.

r:15. A devicesuch as claimed in claim 13, said seat being lined andsaid spherical body being covered with aresilientv material.

References `Cited in the le of Athis patent UNITED STATES PATENTS842,049 Wolsk Jan. 22, 1907 2,388,741 Hays NOV. 13, 1945 2,422,031Mertin June 10, 1947 2,713,472 Bodine July 19, 1955 2,746,721 Moore May22, 1956 2,780,438 Bielstein Feb. 5, 1957

